what is carbonless paper

•  Receipts and invoices: because carbonless carbon paper can be rewritten, so in the production of receipts and invoices can save a lot of carbon pens and carbon stamps, but also to avoid the use of carbon pens or stamps because of the clarity and stability of the problem.
• Prescription and medical records: carbonless paper can be used to produce medical records and prescriptions. This is very convenient for medical records that need to be recorded and revised frequently, reducing the number of times carbon pens and stamps are used, improving work efficiency and reducing costs.
• Document Backup and Printing: Since carbonless paper can be rewritten, it can be used for document backup and printing. This is very useful for organizations and companies that need to back up a large number of paper documents, saving the use of paper and carbon pens.
•  Education and training: Carbonless copy paper can be used for education and training. Using carbonless paper in class can help students to take notes and practice, and it can help teachers to check and record. In addition, it can also be used for handwritten notes and handouts in training courses.
• Logistics and courier: carbonless paper can be used in the logistics and courier industry. Used for receiving and shipping records related information to use, and multiple copies, the sender and receiver, as well as the transportation side, the financial side can be retained a copy.

Carbonless duplicating paper as the first chemical-based pressure-sensitive recording paper, was invented in 1954 by the United States NCR (National Cash Register) company Lowell Schleicher and Barry Green.
Microcapsules on the back of carbonless copy paper. Early microcapsules were prepared by precipitating water-soluble polymers on the surface of organic microemulsion droplets containing dye precursors. The precipitation process was regulated by pH and temperature. The microcapsules were directly about 3 to 8 μm (size depends on the size of the microemulsion droplets). Current microcapsules, prepared by organic polymerization between two-phase interfaces (no longer by the aforementioned mechanism of polymer cross-linking and precipitation), are more controllable. Common 'membranes' for microcapsules are polyurea, polyamide, phenolic resins, and so on.

Dye precursors in microcapsules. It is called a 'precursor' because it must be colorless and must become a colored dye under specific conditions. Common carbonless copy paper has a choice of handwriting colors such as black, blue, orange, green, red, purple, etc., and accordingly, the dye precursors required for them are different.

The color development of these dye precursors is pH regulated. For example, the first dye precursor to be used: crystalline violet lactone, in acidic conditions, the hybridization pattern of the central carbon changes from sp3 to sp2, the entire molecular structure changes to a planar aromatic structure, and its electronic excitation state is shifted from the ultraviolet region to the visible region, i.e., it changes from colorless to colored.

Carbonless paper has a "color-developing layer", or active layer, on the front side of the paper. The active component of the color development layer is the color developer. Common color developers can be divided into three categories: clay-based, organic (e.g., phenolic resins), and metal salts of aromatic carboxylic acids (e.g., zinc salicylate). All of these color developers act as proton donors.